1. Field of the Invention
This invention relates to a passive (i.e., no moving parts) dispenser for storing and issuing a predetermined amount of a solution into a toilet tank. More particularly, the present invention relates to a passive dispenser having a double air vent system and in which the solution to be dispensed is substantially isolated from the tank water by means of a hydrostatic pressure gradient directed towards the solution.
2. Description of the Prior Art
Devices for dispensing a disinfectant solution into a toilet tank for flow into the toilet bowl when the toilet tank is flushed are known. It is generally desirable to isolate the disinfectant from the water in the toilet tank during quiescent periods. It is known to use valves or other mechanisms which will shut off flow from the dispenser when the toilet tank is filled to a desired level. See, for example, U.S. Pat. Nos. 1,307,535; 2,682,165; 3,073,488; 3,341,074; 3,698,021; 3,778,849; 3,784,058; 3,895,739; and 4,036,407.
Passive dispensers which are devices having no moving parts are also known. In one type of such passive dispensers, the dispensers are alternately flooded and then siphoned when the tank is flushed. See, for example, U.S. Pat. Nos. 650,161; 1,144,525; 1,175,032; 1,213,978; and 3,339,801. In another type, the dispensers are alternately flooded and then drained gravitationally. See, for instance, U.S. Pat. Nos. 1,987,689; 3,121,236; 3,504,384; 3,545,014; 3,618,143; 3,604,020; 3,772,715; 3,781,926; 3,943,582; and 4,244,062. In addition, U.S. Pat. Nos. 2,688,754; 3,864,763; and 3,965,497 and U.K. Pat. No. 705,904 disclose toilet chemical dispensers in which a small amount of the chemical is released into the tank in the absence of hydrostatic pressure on the spout thereof, e.g. when the toilet has been flushed and the water level in the tank has dropped. As the tank becomes filled with water, the resulting hydrostatic head prevents the solution from being released from the dispenser. In a further type of passive dispenser, the solution to be dispensed is connected to a pressurized water supply such as the trap refill pipe in a toilet tank. See, for example, U.S. Pat. Nos. 3,407,412 and 3,444,566 wherein the direction of flow alternates in labyrinth passages. In all of the above mentioned passive dispensers, due to the construction thereof, the disinfectant can flow or diffuse into the toilet tank water.
Passive dispensers using air locks, i.e. pockets of air, to isolate the disinfectant from the water during quiescent periods in a toilet tank have been disclosed. For instance, U.S. Pat. Nos. 4,171,546 and 4,216,027 disclose passive dispensers which issue a predetermined volume of a toilet tank additive solution into a toilet tank as the water is draining therefrom when the toilet is flushed. According to these patents, an amount of a concentrated additive solution is drawn from a storage place into the tank as the water level therein drops resulting from flushing. The devices are provided with numerous baffles and passageways to form air locks which isolate the concentrated disinfectant solution from the tank water when the toilet tank is in a quiescent state. In these devices, the air locks are located at the top of the device. U.S. Pat. No. 4,186,856 discloses a passive dispenser having air locks formed in the top portion thereof when submerged to isolate the tank water from the concentrated disinfectant stored therein. Other passive dispensers are disclosed in U.S. Pat. Nos. 4,208,747, 4,305,162 and 4,307,474 wherein air locks are also employed to isolate the disinfectant from tank water during quiescent periods. However, the air locks in these patents are disposed at different levels whereas those employed in U.S. Pat. Nos. 4,171,546; 4,186,856 and 4,216,027 are at the same level and in the top portion thereof. U.S. Pat. No. 4,251,012 discloses another passive dispenser in which a concentrated disinfectant is issued into a toilet tank in measured quantities. Although air locks are also used to isolate the disinfectant from the tank water, this device is so constructed that the disinfectant is stored in a compartment which is not accessible to the tank water, even when the device is completely submerged. The air locks provided are located at the same level near the top portion thereof. U.S. Pat. No. 4,281,421 discloses a dispenser having separate compartments for storing individual components for toilet tank additives.
None of the above mentioned patents discloses or suggests a passive dispenser wherein the solution to be dispensed is substantially isolated from the water in the toilet tank by means of a hydrostatic head gradient which is directed toward the solution. In addition, none of the above mentioned patents teaches or suggests a dispenser having a double air vent system, one of the vents provided with a constriction to modify equilibrium hydraulic head forces during the flush/refill cycle.